Shale oil reservoir brittleness evaluation method based on stratification structure

Abstract

The present application provides a kind of shale oil reservoir brittleness evaluation method based on bedding structure, comprising: step 1, collecting the well logging curve of shale oil well, rock mechanics parameter, the measured content of main mineral of shale;Step 2, the mineral content of shale oil reservoir is modeled using multiple regression method, to predict the brittleness mineral content of shale oil well and other shale minerals;Step 3, the brittleness index of shale oil reservoir is solved using the brittleness mineral content of shale oil reservoir;Step 4, the brittleness index of shale oil reservoir is calculated using the ratio of Young's modulus and Poisson's ratio of mixed mineral;Step 5, the bedding development indication of shale oil is calculated using the ratio of P-wave and S-wave of acoustic wave;Step 6, the brittleness of shale oil reservoir is evaluated.The shale oil reservoir brittleness evaluation method based on bedding structure breaks through the limitation of single solution, considers the real situation of strong heterogeneity of shale oil reservoir at the same time, has strong practicability, and has high evaluation reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oilfield development, and particularly relates to a shale oil reservoir brittleness evaluation method based on a bedding structure. BACKGROUND

[0002] Based on the characteristics of shale oil, such as complex lithology, various storage modes, ultra-low porosity and permeability, and strong heterogeneity, the "four-property" relationship research (reservoir property, oiliness, compressibility, and mobility) is generally used to optimize shale oil "dessert" with characteristics of large reservoir thickness, strong seepage capacity, high organic matter content, high brittle mineral content, and strong compressibility. In the "four-property" relationship research of shale oil, compressibility is a necessary condition for determining the target and targeting, so the compressibility, i.e., the brittleness index, is determined to ensure the drilling rate of favorable lithofacies. The brittleness evaluation of shale can help fracturing reconstruction, energy increase and production increase, and improve the recovery rate to maximize the EUR of single well, and realize CO2 storage and practice the win-win situation of green and low-carbon development. Therefore, it is very important to propose a calculation method for fine evaluation of the brittleness index of shale oil reservoirs to enrich the theory and technology system of continental shale oil exploration and development.

[0003] At present, there are two methods for evaluating the brittleness of shale oil reservoirs. One is to solve the brittleness of minerals, and the other is to solve the rock mechanics parameters (Young's modulus and Poisson's ratio). The two commonly used methods do not consider the real situation of shale oil reservoirs. The shale oil reservoirs in the research area of the Dongying Sag have the characteristics of complex lithology, strong heterogeneity, ultra-low porosity and permeability, and various storage modes, which makes it difficult to characterize the brittleness by using conventional brittleness evaluation methods. Therefore, there is an urgent need for a brittleness evaluation method for shale oil reservoirs with deep burial, strong heterogeneity, complex rock mineral composition, and various pore types.

[0004] In the Chinese patent application with the application number CN202110408102.7, a rock brittleness evaluation method based on drilling rock cuttings logging data is disclosed, which includes the following steps: step 1, obtaining three-dimensional digital core micro parameters from drilling rock cuttings logging data of the well to be measured; step 2, generating a three-dimensional digital core sample according to the obtained drilling rock cuttings micro parameters; step 3, performing uniaxial or triaxial compression numerical experiments on the three-dimensional digital core sample to obtain the stress-strain curve of the three-dimensional digital core, and calculating the elastic modulus and Poisson's ratio of the core; step 4, calculating the normalized elastic modulus, Poisson's ratio, and proportion of brittle minerals; step 5, calculating the brittleness index considering the rock mineral composition and mechanical properties; and step 6, selecting drilling rock cuttings at different depths of the well to be measured, repeating steps 1 to 5, and calculating the rock brittleness index continuously distributed along the well depth of the reservoir section. The invention does not need coring operation, and comprehensively considers the influence of brittle mineral composition and rock elastic parameters on brittleness, so the evaluation result of reservoir rock brittleness is more accurate.

[0005] In the Chinese patent application with the application number: CN201810269812.4, a method for evaluating the brittleness of tight sandstone reservoir rock is disclosed, which comprises the following steps: 1) obtaining the core brittleness index of the target layer section of the tight sandstone; 2) obtaining the rock mineral component content of the target layer section of the tight sandstone; 3) determining the brittleness mineral of the target layer section of the tight sandstone; 4) obtaining the rock brittleness index of each depth point of the target layer section of the tight sandstone; and 5) evaluating the fracturability of the tight sandstone reservoir according to the rock brittleness index of each depth point of the target layer section of the tight sandstone and the results of the formation fracturing. The present application can effectively avoid the errors caused by the difference in the determination of the brittleness mineral and the equal weight, and is efficient, fast, small in calculation error and strong in universality.

[0006] In the Chinese patent application with the application number: CN201410790723.6, a method for evaluating the brittleness of shale reservoir is disclosed, which belongs to the technical field of unconventional oil and gas reservoir evaluation. The method comprises the following steps: obtaining the elastic parameters and brittleness mineral parameters of the shale reservoir to be evaluated, the elastic parameters including Young's modulus and density; performing cross analysis on the Young's modulus and density and other elastic parameters and / or brittleness mineral parameters, and determining the value range of the Young's modulus and density according to the results of the cross analysis; constructing a Young's modulus and density attribute volume according to the P-wave and S-wave impedances obtained through pre-stack inversion; and evaluating the brittleness of the shale reservoir to be evaluated within the value range of the Young's modulus and density attribute volume. The present application improves the evaluation accuracy of the brittleness of the shale reservoir, realizes the prediction of the planar distribution of the brittleness of the entire research area, and has a wide application prospect in the field of shale gas exploration and development.

[0007] The above prior art has great differences from the present application and cannot solve the technical problems we want to solve. Therefore, we have invented a new shale oil reservoir brittleness evaluation method based on bedding structure. SUMMARY

[0008] The purpose of the present application is to provide a shale oil reservoir brittleness evaluation method based on bedding structure, which integrates the characteristics of the bedding structure of the shale oil reservoir into the brittleness index, has strong practicability and high evaluation reliability.

[0009] The purpose of the present application can be achieved by the following technical measures: a shale oil reservoir brittleness evaluation method based on bedding structure, which comprises the following steps:

[0010] Step 1: collecting the logging curves of the shale oil well, the rock mechanics parameters, and the measured content of the main minerals of the shale;

[0011] Step 2: modeling the mineral content of the shale oil reservoir by using the multiple regression method to predict the brittleness mineral content and other shale mineral content of the shale oil well;

[0012] Step 3, solve the brittleness index of the shale oil reservoir using the brittle mineral content of the shale oil reservoir;

[0013] Step 4, calculate the brittleness index of the shale oil reservoir using the ratio of the Young's modulus and Poisson's ratio of the mixed minerals;

[0014] Step 5, calculate the shale oil lamina development indicator using the ratio of the compressional wave and shear wave of the acoustic wave;

[0015] Step 6, evaluate the brittleness of the shale oil reservoir.

[0016] The purpose of the present application can also be achieved by the following technical measures:

[0017] In step 1, the logging curves of the shale oil well are collected, including the conventional 5 curves, i.e. natural gamma ray GR, deep resistivity RT, acoustic time difference AC, neutron CNL, density DEN, and the compressional wave and shear wave curves Vp and Vs.

[0018] In step 1, the rock mechanics parameters include the Young's modulus YM and Poisson's ratio PR, and the measured content of the main minerals of the shale, including carbonate rock, quartz, feldspar, clay, and dolomite.

[0019] In step 2, the mineral content of the shale oil reservoir is modeled using the multiple regression method, the core and logging curves are corrected and abnormal points are removed, and then the mineral content measured by the whole rock diffraction experiment is matched with the logging curves to optimize the sensitive curve of each mineral; the mineral content of the shale oil reservoir is modeled by segment-by-segment and multiple regression methods to predict the brittle mineral and other shale mineral content of the entire well section of the shale oil well.

[0020] In step 2, the mineral content of the shale oil reservoir includes carbonate rock, quartz, feldspar, clay, and dolomite, the brittle mineral includes carbonate rock, quartz, and feldspar, and the other shale mineral content includes clay and dolomite.

[0021] In step 3, the brittleness index of the shale oil reservoir is solved using the brittle mineral content of the shale oil reservoir; carbonate rock, feldspar, and quartz are taken as the main brittle minerals of the shale oil reservoir, and clay and dolomite are taken as other minerals, and the brittle mineral is used to solve the brittleness index of the shale reservoir.

[0022] In step 3, the formula for solving the brittleness index of the shale reservoir is as follows:

[0023] Brit 脆性矿物 =(V 长石 +V 石英 +V 碳酸盐岩 ) / (V 长石 +V 石英 +V黏土 +V 碳酸盐岩 +V 白云岩 ) (1)

[0024] Brit = E / PR 脆性矿物 Brit is the brittleness index of shale oil reservoir, V 长石 is the feldspar content, V 石英 is the quartz content, V 碳酸盐岩 is the carbonate content, V 白云岩 is the dolomite content, V 黏土 is the clay content.

[0025] In step 4, the brittleness index of shale oil reservoir is calculated by using the ratio of Young's modulus and Poisson's ratio of mixed minerals, and the formula is as follows;

[0026]

[0027]

[0028]

[0029] Brit = E / PR sta E is the Young's modulus of rock, E sta_min is the minimum value of rock Young's modulus in a certain formation section, E sta_max is the maximum value of rock Young's modulus in a certain formation section, V sta is the Poisson's ratio of rock, V sta_min is the minimum value of rock Poisson's ratio in a certain formation section, V sta_max is the maximum value of rock Poisson's ratio in a certain formation section, YM C and PR C Brit is the brittleness index calculated by Young's modulus and Poisson's ratio, Brit 岩石力学 is the brittleness index.

[0030] In step 5, the bedding structure characteristics are considered in the brittleness evaluation of shale reservoir; the ratio of P-wave and S-wave of acoustic wave is used to calculate the development degree of bedding structure of shale oil, according to the principle of P-wave and S-wave propagation, the displacement direction of S-wave particle is perpendicular to the well axis, in bedding and low-angle fracture, part of the energy of S-wave propagates along the bedding and low-angle fracture, thereby causing the propagation velocity of S-wave collected by the instrument to decrease, while the propagation direction and particle displacement direction of P-wave are parallel to the well axis, and the bedding and low-angle fracture have little effect on the velocity of P-wave, so that the ratio of P-wave and S-wave velocity Vp / Vs increases in the place where the bedding and low-angle fracture develop.

[0031] In step 5, the calculation formula of brittleness index is as follows;

[0032] Y 层理结构 = V PV S (5)

[0033] Wherein: Y 层理结构 is the bedding structure of the shale oil reservoir, Vp is a longitudinal wave, and Vs is a transverse wave;

[0034] When the longitudinal-transverse wave velocity ratio Vp / Vs increases, the laminae is more developed, and vice versa, the bedding structure is not developed.

[0035] In step 6, the shale laminae development index solved in step 5 is added to the brittleness index of the shale oil reservoir solved in step 3 and step 4, and the brittleness index can reflect the bedding structure of the shale oil reservoir, and also considers the rock mechanics structure and mineral component composition of the shale.

[0036] In step 6, the formula for evaluating the brittleness of the shale oil reservoir is:

[0037] Brit=(Vp / Vs)*((V 长石 +V 石英 +V 碳酸盐岩 ) / (V 长石 +V 石英 +V 黏土 +V 碳酸盐岩 +V 白云岩 ))*((YM C +PR C ) / 2)(6).

[0038] The shale oil reservoir brittleness evaluation method based on the bedding structure in the application considers the development characteristics of the strong heterogeneity of the shale oil reservoir, integrates the bedding structure characteristics of the shale oil reservoir into the brittleness index, has strong practicability, high evaluation reliability, and provides important technical support for exploration and development of the shale oil.

[0039] Compared with the prior art, the application has the following advantages:

[0040] The brittleness evaluation method is superior to the method for obtaining a single brittleness mineral and the method for evaluating brittleness by using Young's modulus and Poisson's ratio, breaks through the limitation of single solution, considers the real situation of the strong heterogeneity of the shale oil reservoir, has strong practicability, high evaluation reliability, and provides important technical support for exploration and development of the shale oil. DETAILED DESCRIPTION

[0041] Figure 1 is a flow chart of a specific embodiment of the shale oil reservoir brittleness evaluation method based on the bedding structure of the application;

[0042] Figure 2 is a schematic diagram of a conventional shale oil reservoir brittleness evaluation method in a specific embodiment of the application;

[0043] Figure 3 The result map of the shale oil reservoir brittleness evaluation method based on the stratification structure in a specific embodiment of the present application. DETAILED DESCRIPTION

[0044] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0045] It should be noted that the terms used herein are only intended to describe specific embodiments and are not intended to limit exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form unless the context clearly indicates otherwise, and it should also be understood that when the terms "comprise" and / or "include" are used in the specification, they indicate the presence of the features, steps, operations and / or combinations thereof.

[0046] The shale oil reservoir brittleness evaluation method based on the stratification structure of the present application includes the following steps:

[0047] Step 1, collect the well logging curves of the shale oil well, the rock mechanics parameters, and the measured content of the main minerals of the shale, including carbonate rock, quartz, feldspar, clay, and dolomite;

[0048] Step 2, use the multiple regression method to model the mineral content of the shale oil reservoir to predict the brittle mineral content and other shale mineral content of the shale oil well;

[0049] Step 3, use the brittle mineral content of the shale oil reservoir to solve the brittleness index of the shale oil reservoir;

[0050] Step 4, use the ratio of the Young's modulus and Poisson's ratio of the mixed minerals to calculate the brittleness index of the shale oil reservoir;

[0051] Step 5, use the ratio of the compressional wave and shear wave of the acoustic wave to calculate the laminated development indicator of the shale oil;

[0052] Step 6, according to the development characteristics of the strong heterogeneity of the shale oil reservoir, add the laminated development indicator to the brittleness index of the shale oil reservoir solved in steps 3 and 4 to obtain a new shale oil reservoir brittleness evaluation method.

[0053] The following are several specific embodiments of the application

[0054] Example 1

[0055] In a specific embodiment 1 of the application, the shale oil reservoir brittleness evaluation method based on the stratification structure comprises the following steps:

[0056] In step 1, the logging curves of the shale oil well are collected, including conventional 5 curves (natural gamma GR, deep resistivity RT, acoustic time difference AC, neutron CNL, density DEN) and P and Vs curves, rock mechanics parameters (Young's modulus YM and Poisson's ratio PR), and the measured content of main minerals of the shale, including carbonate rock, quartz, feldspar, clay, and dolomite;

[0057] In step 2, the mineral content of the shale oil reservoir is modeled by using the multiple regression method, the core and logging curves are corrected and the abnormal points are removed, and the mineral content measured by the whole rock diffraction experiment is matched with the logging curves to optimize the sensitive curve of each mineral. The mineral content (carbonate rock, quartz, feldspar, clay, and dolomite) of the shale oil reservoir is modeled by using the segment-to-segment and multiple regression methods, and the brittle mineral content (carbonate rock, quartz, and feldspar) and other shale mineral content (clay and dolomite) of the entire well section of the shale oil well are predicted;

[0058] In step 3, the brittleness index of the shale oil reservoir is solved by using the brittle mineral content of the shale oil reservoir; the carbonate rock, feldspar, and quartz are taken as the main brittle minerals of the shale oil reservoir, and the clay and dolomite are taken as other minerals, and the brittle mineral is used to solve the brittleness index of the shale reservoir, and the formula is as follows:

[0059] Brit 脆性矿物 =(V 长石 +V 石英 +V 碳酸盐岩 ) / (V 长石 +V 石英 +V 黏土 +V 碳酸盐岩 +V 白云岩 ) (1)

[0060] Wherein: Brit 脆性矿物 is the brittleness index of the shale oil reservoir, V 长石 is the feldspar content, V 石英 is the quartz content, V 碳干活酸盐岩 is the carbonate rock content, V 白云岩 is the dolomite content, and V 黏土 is the clay content;

[0061] In step 4, the brittleness index of the shale oil reservoir is calculated by using the ratio of the Young's modulus and Poisson's ratio of the mixed mineral, and the formula is as follows:

[0062]

[0063]

[0064]

[0065] where: E sta is the Young's modulus of the rock, E sta_min is the minimum value of the Young's modulus of the rock within a certain formation interval, E sta_max is the maximum value of the Young's modulus of the rock within a certain formation interval, V sta is the Poisson's ratio of the rock, V sta_min is the minimum value of the Poisson's ratio of the rock within a certain formation interval, V sta_max is the maximum value of the Poisson's ratio of the rock within a certain formation interval, YM C and PR C is the brittleness index calculated by the Young's modulus and the Poisson's ratio, Brit 岩石力学 is the brittleness index;

[0066] In step 5, because the shale oil reservoir is complex and diversified, the bedding structure is different, the reservoir space and the reservoir capacity are different, such as the existence of homogeneous and heterogeneous in the same interval of marl interbed, and the development of bedding structure may be uneven in thickness, so the bedding structure characteristics should be considered in the brittleness evaluation of the shale reservoir. The development degree of the bedding structure of the shale oil is calculated by the ratio of the compressional wave and the shear wave of the acoustic wave. According to the propagation principle of the compressional wave and the shear wave, the displacement direction of the shear wave particle is perpendicular to the well axis, and in the bedding and low-angle fracture, part of the energy of the shear wave propagates along the bedding and low-angle fracture, thereby causing the propagation velocity of the shear wave collected by the instrument to decrease, while the propagation direction and the particle displacement direction of the compressional wave are parallel to the well axis, and the bedding and low-angle fracture have little effect on the velocity of the compressional wave. Therefore, in the place where the bedding and low-angle fracture are developed, the ratio of the compressional wave velocity and the shear wave velocity Vp / Vs increases, and the formula is as follows.

[0067] Y 层理结构 = V P / V S (5)

[0068] where: Y 层理结构 is the bedding structure of the shale oil reservoir, Vp is the compressional wave, and Vs is the shear wave.

[0069] When the ratio of the compressional wave velocity and the shear wave velocity Vp / Vs increases, the laminae is more developed, and vice versa, the bedding structure is not developed.

[0070] In step 6, the shale lamina development index solved in step 5 is added to the brittleness index of the shale oil reservoir solved in step 3 and step 4, the brittleness index proposed in the patent can reflect the bedding structure of the shale oil reservoir, and also considers the rock mechanics structure and mineral component composition of the shale, so that a new brittleness evaluation method suitable for the shale oil reservoir is obtained;

[0071] Brit = (Vp / Vs) * ((V 长石 + V 石英 + V 碳酸盐岩 ) / (V 长石 + V 石英 + V 黏土 + V 碳酸盐岩 + V 白云岩 ))*((YM C + PR C ) / 2) (6)

[0072] Embodiment 2

[0073] In a specific embodiment 2 of the application, the purpose layer section (Shan 4 pure upper) of the shale oil well in the Niuzhuang depression of the Dongying sag in Shengli oilfield is taken as an example to illustrate the specific implementation of the calculation method.

[0074] As Figure 1 shown, the shale oil reservoir brittleness evaluation method based on the bedding structure comprises the following steps:

[0075] In step 1, the logging curves of the shale oil well in the study area are collected, including the conventional 5 curves (natural gamma GR, deep resistivity RT, acoustic time difference AC, neutron CNL, and density DEN) and the P and S wave curves (Vp and Vs), the measured content of the main minerals of the shale oil reservoir obtained by the whole rock diffraction experiment, including carbonate rock, felsic sandstone (quartz, feldspar), clay, and dolomite;

[0076] In step 2, the mineral content of the shale oil reservoir is modeled by using the multiple regression method.

[0077] The core and logging curves are corrected and abnormal points are removed to ensure a certain data quality.

[0078] The mineral content measured by the whole rock diffraction experiment is matched with the logging curves to optimize the sensitive curve of each mineral. The resistivity RT is greatly affected by the formation water salinity and the formation environment, so the curve is removed. It is found that the measured basic mineral content in the study area has good correlation with the logging curves of natural gamma (GR), acoustic time difference (AC), density (DEN), and neutron (CNL), so the four sensitive new curves are selected.

[0079] Through the segment by segment, the quality of the data points on and off 0.5 meters range of all data points to take the average value, to ensure the reliability of the mineral content model.

[0080] Using multiple regression method, the mineral content of shale oil reservoir (carbonate, felsic sandstone (quartz, feldspar), clay, dolomite) data fitting, stratified prediction of the purpose of the study area Niu Zhuang sag shale oil well layer (pure upper 1, pure upper 2, pure upper 3) brittle mineral content (carbonate, felsic sandstone (quartz, feldspar)) and other shale mineral content (clay, dolomite), the formula is as follows;

[0081] Clay content (pure upper 1) = -79.61 + 0.62*GR-0.29*AC+29.11*DEN+1.02*CNL

[0082] Clay content (pure upper 2) = 80.93 + 0.07*GR-3.47*AC+40.11*DEN+7.34*CNL

[0083] Clay content (pure upper 3) = -65.21-0.23*GR+0.71*AC+227.51*DEN+2.23*CNL

[0084] Carbonate content (pure upper 1) = 95.26-1.58*GR+1.17*AC+50.33*DEN-0.52*CNL

[0085] Carbonate content (pure upper 2) = 13.01-0.48*GR-1.19*AC-41.73*DEN-3.78*CNL

[0086] Carbonate content (pure upper 3) = 88.28+0.04*GR-0.79*AC-27.10*DEN-4.02*CNL

[0087] Felsic sandstone content (pure upper 1) = 24.98+0.17*GR+0.19*AC+72.81*DEN+0.81*CNL

[0088] Felsic sandstone content (pure upper 2) = 34.78+0.37*GR+0.23*AC+26.52*DEN+0.33*CNL

[0089] Felsic sandstone content (pure upper 3) = 23.78+0.27*GR-0.02*AC+86.76*DEN+1.04*CNL

[0090] Dolomite content (pure 1) = 57.58 - 0.07*GR - 1.29*AC - 174.44*DEN - 0.28*CNL

[0091] Dolomite content (pure 2) = 43.93 - 0.19*GR + 0.42*AC + 15.97*DEN + 0.87*CNL

[0092] Dolomite content (pure 3) = 32.19 - 0.34*GR - 1.70*AC - 75.74*DEN + 2.78*CNL

[0093] In step 3, the brittleness index of the shale oil reservoir is solved by using the brittle mineral content of the shale oil reservoir; the content of carbonate rock and felsic sandstone (feldspar, quartz) in the Niuzhuang Sag of the Dongying Depression is relatively high, which can reach about 40%-50% and 20%-30%, which can be used as the main brittle mineral of the shale oil reservoir, and clay and dolomite are used as other minerals. The brittleness index of the shale reservoir is solved by using the brittle mineral, and the formula is as follows:

[0094] Brit 脆性矿物 = (V 长石 + V 石英 + V 碳酸盐岩 ) / (V 长石 + V 石英 + V 黏土 + V 碳酸盐岩 + V 白云岩 )(1)

[0095] Wherein: Brit 脆性矿物 is the brittleness index of the shale oil reservoir, V 长石 is the feldspar content, V 石英 is the quartz content, V 碳干活酸盐岩 is the carbonate rock content, V 白云岩 is the dolomite content, and V 黏土 is the clay content.

[0096] In step 4, the brittleness index of the shale oil reservoir is calculated by using the ratio of the Young's modulus and Poisson's ratio of the mixed mineral of the reaction shale oil reservoir, and the formula is as follows:

[0097]

[0098]

[0099]

[0100] Wherein: E sta is the Young's modulus of the rock, E sta_min is the minimum value of the Young's modulus of the rock in a certain stratigraphic section, and Esta_max Maximum value of Young's modulus of rock in a certain formation section, V sta Poisson's ratio of rock, V sta_min Minimum value of Poisson's ratio of rock in a certain formation section, V sta_max Maximum value of Poisson's ratio of rock in a certain formation section, YM C and PR C Brittleness index calculated by Young's modulus and Poisson's ratio, Brit 岩石力学 Brittleness index;

[0101] In step 5, because the shale oil reservoir is complex and diversified in argillaceous and calcareous interbedded mud interbeds, the bedding structures are different, and the reservoir space and capacity are different, for example, the homogeneous and heterogeneous conditions exist in the argillaceous and calcareous interbedded mud interbeds of the same section, and the bedding structure development thickness may also exist, so the bedding structure characteristics are considered in the shale reservoir brittleness evaluation. The bedding structure development degree of shale oil is calculated by using the ratio of compressional wave and shear wave of acoustic wave. According to the principle of longitudinal wave and transverse wave propagation, the displacement direction of transverse wave particle is perpendicular to the well axis. In the bedding and low-angle fracture, part of the energy of transverse wave propagates along the bedding and low-angle fracture, thereby causing the transverse wave propagation velocity collected by the instrument to decrease, while the propagation direction and particle displacement direction of longitudinal wave are parallel to the well axis, and the bedding and low-angle fracture have little effect on the velocity of longitudinal wave. Therefore, in the place where the bedding and low-angle fracture develop, the ratio of longitudinal wave velocity and transverse wave velocity Vp / Vs increases, and the formula is as follows.

[0102] Y 层理结构 = V P / V S (5)

[0103] Wherein: Y 层理结构 is the bedding structure of shale oil reservoir, Vp is longitudinal wave, and Vs is transverse wave.

[0104] When the ratio of longitudinal wave velocity and transverse wave velocity Vp / Vs increases, the laminations develop more, and vice versa, the bedding structure does not develop;

[0105] In step 6, the shale laminations development indication solved in step 5 is added to the brittleness index of shale oil reservoir solved in step 3 and step 4, so that the new brittleness index can reflect the bedding structure of shale oil reservoir, and the rock mechanics structure and mineral component composition of shale are also considered, so a new brittleness evaluation method suitable for shale oil reservoir is obtained

[0106] Brit = (Vp / Vs) * ((V 长石 + V 石英 + V 碳酸盐岩 ) / (V 长石 + V 石英 + V 黏土 + V 碳酸盐岩 + V白云岩 ))*((YM C +PR C ) / 2)(6)

[0107] Brit = (Vp - Vs) / (Vp + Vs) where Brit is brittleness index, Vp is P-wave, Vs is S-wave; V 长石 is feldspar content, V 石英 is quartz content, V 碳酸盐岩 is carbonate content, V 白云岩 is dolomite content, V 黏土 is clay content; YM C and PR C are brittleness indexes calculated by Young's modulus and Poisson's ratio.

[0108] Embodiment 3

[0109] In a specific embodiment 3 of the application, taking the research area N55-X1 as an example, according to two conventional brittleness evaluation methods, brittleness indexes are calculated by using brittleness mineral content and Young's modulus and Poisson's ratio rock mechanics, and applied in N55-X1 well. The results prove that the brittleness index curves of the shale oil well objective section are not fluctuated and cannot be distinguished, as shown in Figure 1. Because the shale oil reservoir has developed laminations, the bedding structure is complex and diverse, and the thickness is not uniform. In order to solve this problem, the shale oil reservoir brittleness evaluation method based on bedding structure of the application considers the real situation of strong heterogeneity of shale oil reservoir, has strong practicability and high evaluation reliability, integrates the bedding structure into the brittleness index formula, reflects the influence of brittleness mineral content and rock mechanics, considers the bedding structure of shale oil reservoir, is more in line with the real situation of shale oil reservoir, and can obviously see that the brittleness of pure 2 is better, and pure 1 and pure 3 are poor, as shown in Figure 2. Figure 2 Figure 3

[0110] The shale oil reservoir brittleness evaluation method based on bedding structure of the application is superior to the single brittleness mineral evaluation method and the Young's modulus and Poisson's ratio evaluation brittleness method used in the current shale oil reservoir exploration, breaks through the limitation of single solution, considers the real situation of strong heterogeneity of shale oil reservoir, has strong practicability and high evaluation reliability, and provides important technical support for shale oil exploration and development.

[0111] ​​Finally, it should be noted that the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art will appreciate that modifications or equivalent substitutions can be made to the technical solutions described in the foregoing embodiments, or some technical features can be replaced by equivalent features. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

[0112] All features not described in the specification are known to those skilled in the art.

Claims

1. A method for evaluating the brittleness of a shale oil reservoir based on a stratigraphic structure, characterized by, The shale oil reservoir brittleness evaluation method based on the bedding structure comprises: Step 1, collecting the logging curves of the shale oil well, the rock mechanics parameters, and the measured content of the main minerals of the shale; Step 2, modeling the mineral content of the shale oil reservoir by using the multiple regression method, and predicting the brittle mineral content and other shale mineral content of the shale oil well; Step 3, solving the brittleness index of the shale oil reservoir by using the brittle mineral content of the shale oil reservoir; Step 4, calculating the brittleness index of the shale oil reservoir by using the ratio of the Young's modulus and the Poisson's ratio of the mixed minerals; Step 5, calculating the bedding development indication of the shale oil reservoir by using the ratio of the compressional wave and the shear wave of the acoustic wave; Step 6, evaluating the brittleness of the shale oil reservoir; In step 6, the bedding development indication solved in step 5 is added to the brittleness index of the shale oil reservoir solved in steps 3 and 4.

2. The method for evaluating the brittleness of a shale oil reservoir based on a stratigraphic structure according to claim 1, characterized in that, In step 1, the logging curves of the shale oil well are collected, including the conventional five curves, i.e., the natural gamma ray GR, the deep resistivity RT, the acoustic time difference AC, the neutron CNL, and the density DEN, and the compressional wave Vp and the shear wave Vs.

3. The method for evaluating the brittleness of a shale oil reservoir based on a stratigraphic structure according to claim 1, characterized in that, In step 1, the rock mechanics parameters include the Young's modulus YM and the Poisson's ratio PR, and the measured content of the main minerals of the shale, including the carbonate rock, the quartz, the feldspar, the clay, and the dolomite.

4. The method for evaluating the brittleness of a shale oil reservoir based on a stratigraphic structure according to claim 1, characterized in that, In step 2, the multiple regression method is used to model the mineral content of the shale oil reservoir, the core and the logging curve are corrected and the abnormal points are removed, and then the mineral content measured by the whole rock diffraction experiment is matched with the logging curve to optimize the sensitive curve of each mineral; the mineral content of the shale oil reservoir is modeled by using the segment-by-segment and multiple regression methods, and the brittle mineral content and other shale mineral content of the whole well section of the shale oil well are predicted.

5. The method for evaluating the brittleness of a shale oil reservoir based on a stratigraphic structure according to claim 4, characterized in that, In step 2, the mineral content of the shale oil reservoir includes the carbonate rock, the quartz, the feldspar, the clay, and the dolomite, and the brittle mineral content includes the carbonate rock, the quartz, and the feldspar, and the other shale mineral content includes the clay and the dolomite.

6. The method for evaluating the brittleness of a shale oil reservoir based on a stratigraphic structure according to claim 1, wherein, In step 3, the brittleness index of the shale oil reservoir is solved by using the brittle mineral content of the shale oil reservoir; the carbonate rock, the feldspar, and the quartz are taken as the main brittle minerals of the shale oil reservoir, the clay and the dolomite are taken as the other minerals, and the brittleness index of the shale oil reservoir is solved by using the brittle minerals.

7. The method of claim 6, wherein, In step 3, the formula for solving the brittleness index of the shale oil reservoir is as follows: Brit 脆性矿物 = (V 长石 + V 石英 + V 碳酸盐岩 ) / (V 长石 + V 石英 + V 黏土 + V 碳酸盐岩 + V 白云岩 ) (1) Brit 脆性矿物 Brit is brittleness index of the shale oil reservoir, V 长石 F is feldspar content, V 石英 Q is quartz content, V 碳酸盐岩 C is carbonate content, V 白云岩 D is dolomite content, V 黏土 Cl is clay content.

8. The method for evaluating the brittleness of a shale oil reservoir based on a stratigraphic structure according to claim 7, characterized in that, In step 4, the brittleness index of the shale oil reservoir is calculated by using the ratio of the Young's modulus and the Poisson's ratio of the mixed minerals, and the formula is as follows: where: E sta is the Young's modulus of the rock, E sta_min is the minimum value of the Young's modulus of the rock within a certain formation interval, E sta_max is the maximum value of the Young's modulus of the rock within a certain formation interval, V sta is the Poisson's ratio of the rock, V sta_min is the minimum value of the Poisson's ratio of the rock within a certain formation interval, V sta_max is the maximum value of the Poisson's ratio of the rock within a certain formation interval, YM C and PR C is the brittleness index calculated from the Young's modulus and the Poisson's ratio, Brit 岩石力学 is the brittleness index.

9. The method of claim 8, wherein, In step 5, the bedding structure characteristics are considered in the brittleness evaluation of the shale oil reservoir; the bedding structure development degree of the shale oil reservoir is calculated by using the ratio of the compressional wave and the shear wave of the acoustic wave; according to the propagation principle of the compressional wave and the shear wave, the displacement direction of the shear wave particle is perpendicular to the well axis, in the bedding and low-angle fracture, part of the energy of the shear wave propagates along the bedding and low-angle fracture, thereby causing the propagation velocity of the shear wave collected by the instrument to decrease, and the propagation direction and particle displacement direction of the compressional wave are parallel to the well axis, and the bedding and low-angle fracture have little effect on the velocity of the compressional wave, so that the ratio of the compressional wave velocity and the shear wave velocity Vp / Vs increases in the place where the bedding and low-angle fracture develop.

10. The method of claim 9, wherein, In step 5, the calculation formula of the bedding structure is as follows: Y 层理结构 = V P / V S (5) wherein: Y 层理结构 is the bedding structure of the shale oil reservoir, Vp is the longitudinal wave, and Vs is the transverse wave; When the ratio of longitudinal wave velocity to transverse wave velocity Vp / Vs increases, the laminae develop more, and vice versa, the bedding structure does not develop.

11. The method for bedding plane-based shale oil reservoir friability evaluation of claim 1, wherein, In step 6, the formula for evaluating the brittleness of the shale oil reservoir is: Brit = (Vp / Vs)*((V 长石 +V 石英 +V 碳酸盐岩 ) / (V 长石 +V 石英 +V 黏土 +V 碳酸 Salt Rock +V Dolomite))*((YM C +PR C ) / 2) (6).

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